Ch. 4- Rocks

• Rock: solid mixture of crystals of 1 or more minerals.

Characteristics to Classify Rocks

• Composition: minerals that make up rock

• Texture: size, shape, and positions of the grains in rock

• 1. Fine grained• 2. Medium grained• 3. Coarse grained

Rock Cycle • Rock cycle is a continual process

by which new rock form from old rock material.

• Processes that shape the surface of the earth: –Weathering– Erosion–Deposition– Uplift

Sedimentary Rock• Form by process of erosion and

weathering to break down other rocks into sediment which is deposited and compacted

Sedimentary Rock• 3 types of sedimentary rock: – 1. Clastic Sedimentary rock- forms

when rock or mineral fragments are cemented together • Classified by size of fragments they are

made of – 2. Chemical Sedimentary rock: form

from solutions of dissolved minerals and water• Crystallize out of solutions- EX- salt

water

– 3. Organic- forms from remains of plants and animals that cement together• EX- limestone

• Sedimentary structures include:– Ripple marks–Mud cracks– Raindrop impressions

Metamorphic Rock• “meta”= change• “morphos”= shape

• Structure, texture, or composition has changed.

• Most common metamorphic change is caused by pressure

Texture of Metamorphic Rock

• Foliated metamorphic rocks- mineral crystals aligned in planes or bands

• Non-foliated metamorphic rocks- not aligned crystals

• Metamorphic structures are caused by deformation.

2 Types of Metamorphism

• 1. Contact Metamorphism: when a rock comes on contact w/ magma or heat from magma.–Only occurs next to igneous

intrusions• 2. Regional Metamorphism:

enormous pressure b/w deeply buried rock or when crusts collide causing heat and the pressure to change rock.

Igneous Rock• Igneous comes from the Latin

word “fire”• Form when magma cools and

hardens• Texture is determined by rate at

which the rock cools

• Igneous rock that solidifies at Earth’s surface- extrusive

• Igneous rock that solidifies within earth’s surface- intrusive

• Common shapes of intrusive igneous bodies: – Batholiths– Stocks– Sills–Dikes

• Classifying Igneous Rock:• 1. Felsic:– Light colored– Less dense– Rich in silicon, aluminum, sodium,

potassium• 2. Mafic:–Dark colored–More dense– Rich in iron, magnesium, calcium